A tip on the hat to Grist for pointing out an article from Environmental Research Letters from Ken Caldeira and Nathan Myhrvold, on, essentially, how quickly transitioning to clean energy can combat climate change, the inertia inherent in the climate system, and whether anything short of a wholesale rapid transition away from fossil fuels will do the trick.

Here's the academic bottom line:

It appears that there is no quick fix; energy transitions are intrinsically slow. During a transition, energy is used both to create new infrastructure and to satisfy other energy demands, resulting in additional emissions. These emissions have a long legacy due to the long lifetime of CO2 in the atmosphere and the thermal inertia of the oceans. Despite the lengthy time lags involved, delaying rollouts of low-carbon-emission energy technologies risks even greater environmental harm in the second half of this century and beyond. This underscores the urgency in developing realistic plans for the rapid deployment of the lowest-GHG-emission electricity generation technologies. Technologies that offer only modest reductions in emissions, such as natural gas and—if the highest estimates from the life-cycle analyses ... are correct—carbon capture storage, cannot yield substantial temperature reductions this century. Achieving substantial reductions in temperatures relative to the coal-based system will take the better part of a century, and will depend on rapid and massive deployment of some mix of conservation, wind, solar, and nuclear, and possibly carbon capture and storage.

And the more colloquial, blunt one:

When it comes to preventing continued climate change natural gas is simply no solution—despite industry and government enthusiasm for it. To slow warming (which won't happen until the second half of this century but will happen) we need not lower carbon energy sources but truly low carbon ones, and actual energy conservation—that is using less of it.

To put a nail in natural gas as bridge fuel away from coal, here's Myhrvold on the effect of rapidly replacing coal with natural gas on temperatures over the next 100 years:

You have to use the energy system of today to build the new-and-improved energy system of tomorrow, and unfortunately that means creation more emission in the near-term than we would otherwise. So we incur a kind of emission debt in making the transition to a better system, and it can take decades to pay that off. Meanwhile, the temperature keeps rising.

If countries were to start right away and build really fast, so that they installed a trillion watts of gas-fired electricity generation steadily over the next 40 years, that would still add about half a degree Fahrenheit to the average surface temperature of the Earth in 2112—that's within a tenth of a degree of the warming that coal-fired plants would produce by that year. (Carnegie Institution for Science)